A client device in a television-based system can receive video and audio content from a program distributor in the form of broadcast programs, such as news programs, sitcoms, movies, sporting events, commercials, and any other type of television-based information. A client device includes, for example, a set-top box, a digital satellite receiver, a cable box, a digital video recorder (DVR), and a television with a built-in receiver.
To tune channels in existing systems, such as digital cable television systems, a viewer tunes to a particular channel and the client device (e.g., cable box) looks up the requested channel in a channel map to identify a program identifier (PID) associated with the requested channel. The program identifier is used by the client device to receive the requested channel. PID information can change on an irregular basis. For example, channels may be added or deleted, or the bandwidth assigned to a particular channel may change, which may require a rearrangement of channels to accommodate the changed bandwidth. Other changes include changes include addition or deletion of a foreign language audio version of the soundtrack associated with the video content.
If a client device does not contain the current PID information, the client device may not tune the correct channel. To avoid this situation, existing systems receive channel information (including a current channel map) from, for example, a headend on a regular basis. This channel information is typically broadcast by the headend to all client devices capable of receiving data from the headend. The channel information is then stored in the client device. Thus, the client device needs to have a memory device, such as a persistent memory device, capable of storing all channel information. Including such a memory device in a client device increases the cost and complexity of the client device.
If a client device is not powered on or not connected to a communication line (e.g., cable) when a updated channel information is broadcast by the headend, the client device will not receive the updated channel information. Instead, the client device will continue using old channel information, which may cause the client device to improperly tune one or more channels.